This invention relates in general to couplings for tubes and similar fluid conduits and in particular to an improved structure for a quick connect coupling adapted for use with such tubes.
Flexible tubes or hoses are commonly used as fluid conduits in many different fluid power systems. For example, tubes are commonly used to carry pressurized air in vehicle air brake and air conditioning systems. A coupling is provided to connect the end of such a tube to a body, such a conventional fitting, valve, manifold, or similar device adapted to transmit or receive the pressurized air. Many different coupling structures are known in the art. However, connecting the tube to the body (and subsequently removing it therefrom) can be a time consuming and expensive task. Furthermore, such connection and removal is often performed in the field, where specialized tools may not be readily available.
As a result, a wide variety of push-to-connect type couplings have been developed which permit a tube to be quickly and easily connected to a body without the use of tools. In such couplings, the tube is connected to the body simply by installing the coupling in a bore formed in the body (typically by press fitting the coupling therein), then inserting the leading edge of the tube into the coupling. The coupling typically contains a plurality of components for releasably retaining the tube therein. This type of coupling is advantageous because no tools or other manual operations are required to connect the tube to the coupling.
A typical push-to-connect coupling includes a hollow cylindrical sleeve which is press fit or otherwise retained in a bore formed through the body. The sleeve includes an inner surface having a frusto-conical portion formed thereon. A generally hollow cylindrical collet is disposed within the sleeve. The collet is typically partially split so as to have a plurality of flexible fingers. Each of the fingers is provided with an outer frusto-conical surface which cooperates with the inner frusto-conical surface of the sleeve. Each of the fingers is further provided with one or more radially inwardly extending teeth.
A tube is connected to the body by inserting the leading edge thereof into the coupling. The outer surface of the tube engages the fingers, flexing them radially outwardly toward the corresponding inner frusto-conical surface of the sleeve. If the tube is subsequently attempted to be withdrawn from the body, the outer frusto-conical surface of the collet is drawn into engagement with the inner frusto-conical surface of the sleeve. As a result, the radially inwardly extending teeth of the collet fingers are moved into engagement with the outer surface of the tube, preventing the withdrawal thereof.
Under normal operating conditions, the above-described push-to-connect coupling is satisfactory to retain the tube within the coupling and the body. However, if the axial load on the tube is excessive, such as may result from high fluid pressure within the tube, the tube may undesirably be withdrawn from the coupling. Also, if a radial load is placed on the tube, the collet may be displaced from its preferred co-axial position relative to the tube and the sleeve. Such radial displacement can result in leakage from the coupling. Accordingly, it would be desirable to provide an improved push-to-connect type coupling wherein the tube is positively retained within the body, and wherein leakage of fluid from the coupling is minimized, even when radial loads are placed on the tube.